No manslaughter charges will be taken after California collapses killed six students and injured seven.Twitter

Criminal investigators have been carrying out detailed testing at the Library Gardens apartment complex in Berkeley, CA, where a balcony collapse claimed six students lives and seriously injured seven others, in June 2015.

“Destructive testing” on the balcony and relevant materials have been sent to an independent laboratory for forensic testing. Alameda District Attorney’s is working to determine what caused the extensive water damage that led to the balcony's collapse. This investigation is the first of its kind carried out by the DA’s office.

DA investigators, representatives of the victims' families, the building owner and various construction and maintenance companies were invited to observe the destructive testing.

Dunleavy said this invitation was to ensure "fairness for any future litigation."

It is anticipated that civil legal actions involving the families of those killed and severally injured by the collapse, the owner of the apartment block, BlackRock, and the construction firm who built it, Segue Construction, will follow.

The balcony collapse just before 1am on June 16, while a group of mainly Irish J-1 visa students were having a party. Among those who died were five Irish J-1 visa student, Eoghan Culligan, Lorcán Miller, Niccolai Schuster, Eimear Walsh, and Olivia Burke, and her Irish-American cousin Ashley Donohoe.

This week scaffolding has been erected around the build to allow for the significant testing. The DA’s office also consulted with several interested parties before beginning this investigation. Assistant DA Kevin Dunleavy said that working with the California Contractors State License Board, the California Architect's Board, and the California Board for Professional Engineers the office has taken on structural engineering, waterproofing, and architecture experts to aid in the investigation. These experts will also study how the Library Gardens complex was constructed.

The collapsed balcony and the one which had been removed from the apartment below for safety reasons in the days after the incident had been kept in separate locations since the tragedy occurred.

In a statement Dunleavy said that both the balcony which collapsed that the one located below have been removed and are being held at a secure location so the experts can examine them.

A forensic analysis was not carried out in the initial investigation by the City of Berkeley officials. This study, carried out at an independent laboratory, will study relevant materials and Dunleavy hopes it will “determine the source of the water intrusion that left the balcony in such an unsafe condition."

Once the testing is carried out and the construction and maintenance documentation acquired the investigators will assess all the information and form an opinion on who could have taken action to avoid this tragic collapse.

City officials previously concluded, in a report published in June, that dry rot caused by water damage led to the collapse of the balcony. Following on from this Alameda County District Attorney Nancy O’Malley announced civil and criminal investigations into the cause of the balcony collapse.

Since the collapse the construction company, Segue, have attempted to restrain against the DA’s investigation. They argue that the damage caused in testing the balconies could be a disadvantage to the company in the future civil actions. A California judge refused their attempt in July.

It has been close to 20 years since a balcony collapse in California has resulted in a criminal prosecution. To be successful criminal neglect will need to be proved, according to the American Injury Attorney Group.